CollectionViewWithDiff_CELL-size

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {
  return 8;
 }

 - (NSInteger)numberOfSectionsInCollectionView:(UICollectionView *)collectionView {
  return 1 ;
 }

 - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
  CHTCollectionViewWaterfallCell *cell =
  (CHTCollectionViewWaterfallCell *)[collectionView dequeueReusableCellWithReuseIdentifier:CELL_IDENTIFIER
                                                                          forIndexPath:indexPath];
  cell.imageView.image = [UIImage imageNamed:self.cats[indexPath.item % 4]];
  return cell;
  }

  - (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath {
   UICollectionReusableView *reusableView = nil;

  if ([kind isEqualToString:CHTCollectionElementKindSectionHeader]) {
  reusableView = [collectionView dequeueReusableSupplementaryViewOfKind:kind
                                                  withReuseIdentifier:HEADER_IDENTIFIER
                                                         forIndexPath:indexPath];
  } else if ([kind isEqualToString:CHTCollectionElementKindSectionFooter]) {
 reusableView = [collectionView dequeueReusableSupplementaryViewOfKind:kind
                                                  withReuseIdentifier:FOOTER_IDENTIFIER
                                                         forIndexPath:indexPath];
}

  return reusableView;
}

#pragma mark - CHTCollectionViewDelegateWaterfallLayout
  - (CGSize)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout *)collectionViewLayout sizeForItemAtIndexPath:(NSIndexPath *)indexPath {
  return [self.cellSizes[indexPath.item % 4] CGSizeValue];
  }
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
  {
CHTCollectionViewWaterfallCell *cell = [collectionView cellForItemAtIndexPath   :indexPath];

IMGVC*vc=[self.storyboard instantiateViewControllerWithIdentifier:@"IMGVC"];
vc.img=cell.imageView.image;
[self.navigationController pushViewController:vc animated:YES];
}